Oil separator apparatus and method for low miscibility refrigerant systems

ABSTRACT

A process for removing oil contamination from refrigerent in a refrigeration system utilizing an oil lubricated, reciprocating piston type condenser unit. The system is characterized by use of heat-cleanable filter tanks mounted in parallel and forming alternating means for scavenging oil from liquid refrigerant, and heating the oil to cause its flow from the filter tank. A cycle timer initiates the defrost cycle at predetermined intervals, such as weekly.

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[ Aug. 14, 1973 01L SEPARATOR APPARATUS AND 2,462,012 2/1949 Vilter 62/470 METHOD FOR LOW MISCHBIILITY gl ifp 2/ /3 i er 6 l 2 REFRIGERANT SYSTEMS 3,336,762 8/1967 Patterson 62/472 [76] Inventor: Joseph R. Simard, 327 Wharf Rd,

Pelham 03076 Primary Examiner-William J. Wye 22 F J 13 1972 Attorney-Pearson & Pearson [2]] Appl. No.: 218,695

[ 5 7] ABSTRACT 52 us. 01. 62/84, 62/192, 62/470, A Process for removing Oil Contamination from refrig- 7 2 erent in a refrigeration system utilizing an oil lubri- 511 1111.01. ..1F25b 43/02 cared, reciprocating Piston yp condenser unil- The 5 n w f Search 62/84, 5 7 470 system is characterized by use of heat-cleanable filter 62/474, 193, 194, 195, 192, 468, 469, 471, tanks mounted in parallel and forming alternating 72 7 means for scavenging oil from liquid refrigerant, and heating the oil to cause its flow from the filter tank. A 5 References Cited cycle timer initiates the defrost cycle at predetermined UNITED STATES PATENTS 7 intervals, such as weekly. 2,097,725 11/1937 Gay 62/192 7 Claims, 1 Drawing Figure TANK RERIGERANT FADE-OUT GAS /24 l 1.10010 i- LEVEL 1 CONTROL 42b AIR SUPPLY 18 v v 5b 40a 40 so SOL 3 i, CONTROL 35a 34a 35b 34b 1 L I ll 350 Q 35b K CONDENSING 1: 32a 32b UNIT 44a 44b sot sot 1 7 j v v 12 H 38a 38b b l9 35(1 Q 50b V 52 V compasssoa CRANKCASE v LIQUlD-- v OIL SEPARATOR APPARATUS AND METHOD IFOR LOW MISCIIBIIILITY REFRIGERANT SYSTEMS FIELD OF THE INVENTION This invention relates to compressor systems, especially compression systems using a reciprocating-piston compressor and an immiscible oil-refrigerant system.

BACKGROUND OF THE INVENTION The number of large compressor systems utilized in refrigeration systems, central air-conditioning systems and the like has increased markedly in the last decade. Indeed, many commercial operations are based on the assumption that the compressor systems will be in operation on demand and are seriously inconvenienced or even shut down when the compressor system is totally or partially down for maintenance.

One of the chief causes of such maintenance is found in oil lubricated, piston-type compressors, especially when they are used in systems utilizing such advantageous refrigerants as those of the low miscibility type, e.g. the refrigerant sold under the trade designation R503 by Allied Chemical Co. or DuPont Co. In these situations, it is usually impossible or impractical for the ordinary facility to maintain a compressor system in such a way that the piston lubricating oil is suitably excluded from the refrigerant carrying conduits of the system. Suchoils tend to seep into and foul refrigerant lines and expensive and inconvenient maintenance work is necessary to remove the oil.

There have been a number of approaches suggested inthe prior art to this general kind of problem. One of the most obvious solutions is simply to use diaphragm- .sealed compressors. However, such compressors often are not utilized because of their considerably greater initial cost.

Oil condensing means have also been suggested for incorporation into the compressor system. Heretofore, these condensing systems have been placed in the hightemperature side of the system and have, consequentiy, required considerable heat absorption to condense the oil. Among such apparatus are those described in U. S. Pat. No. 2,149,358 to Miller and U. S. Pat. Nos. 3,274,796 and 3,283,522 to Kocher. There has continued to be a need for an improved system whereby reciprocating-piston refrigeration systems can be operated continually at the highest thermal efficiency and with the least maintenance cost.

SUMMARY OF THE INVENTION Therefore it is an object of the present invention to provide a refrigeration system, of the type utilizing a reciprocating-piston compressor, which refrigeration system comprises improved means for avoiding oilfouling of the refrigeration lines.

Another object of the invention is to provide a refrigeration system whereby oil consumption is minimized.

A further object of the invention is to provide an oil handling system within a refrigeration loop which is inexpensively maintained and adapted for automatic selfcleaning.

Other objects of the invention will be obvious to those skilled in the art on reading the instant application.

The above objects have been substantially achieved by theconstruction of a refrigerating system of the type that utilizes a reciprocating piston type and wherein a line comprising oil-scavenging traps mounted in parallel is placed in the low temperature, i.e. evaporator, side of the compressor system and advantageously equipped with filter means, and cycle actuating means to enable it to provide the continuouos function of scavenging oil from the system, cleaning the oil and, if desired, returning the oil to the compressor.

This system has been found to reduce maintenance markedly; yet the cost of the system is far below that at which a refrigeration system diaphragm-sealed compressor could be purchased.

ILLUSTRATIVE EXAMPLE OF THE INVENTION For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing which is a diagram ofa refrigeration system of the present invention.

Referring to the drawing, it is seen that refrigeration system MD consists of a condensing unit 12, including a reciprocating piston-type compressor 111 which receives a gaseous refrigerant M from conduit 16 at the inlet side of the condensing unit and discharges a liquid refrigerant 18 from the outlet side of the condensing unit into conduit 119.

The liquid refrigerant is passed through an oil scavenging system 20, thence to a conduit 22 and into a refrigerant hold tank 24 whence liquid refrigerant 18 is passed through evaporator coils 26 of a refrigerated unit proper. Thence the evaporated refrigerant I4 is returned once again to condesning unit 112 through conduit 116. The basic system described above, of course, does not differ in any significant way from ordinary refrigeration systems. The novelty and special advantage of the system lies in the placement, structure and function of the refrigerant-scrubbing system 20.

Referring now to system 20 of the drawing, it is seen that conduit I9 terminates at a T-fitting 30. Thence the refrigerant E8 is carried into one of refrigerantscrubbing tanks 320 or 32b. Each tank 32a or 32b comprises an internal heating means 340 or 34b, an external heating means 35a or 35b, and a mechanical scrubbing means such as a fine steel mesh filter element 36a or 34527. Refrigerant will enter 32a or 32b through one of conduits'38a or 38b, proceed through the tanks 32a or 32b into a conduit 40a or 4191; and thence to con duit 22. Supplementary pressure-relief means 412a or 4212 is to provide an extra measure of safety in the scrubbing system.

In normal operation, liquid refrigerant will flow through a first tank 32a during whichtime it will be mechanically scrubbed of non-miscible oil. This flow of refrigerant is generally responsive to the cooling requirements of the evaporator system as secured by control valve 28 in response to the liquid level in refrigerant tank 241. When a build-up of oil on the filter 36a, in tank 32a is significant, a cycle timer control means 337 will actuate a valve 44a to cut the first tank 32a out of the scavenging system 2@ and cause the liquid refrigerant to flow through a second tank 32b.

While refrigerant is being scrubbed in the second tank 32b, the first tank is reconditioned for its return into the liquid refrigerant recirculation loop at the time the second tank becomes sufficiently contaminated to require reconditioning.

This reconditioning of an oil scavenging unit can be conveniently carried out by utilizing any of a number of procedures.

Each tank 32a r 32b has a control valve 44a or 44b at the inlet side thereof between T-fitting 30 and the tank itself. Each tank 32a or 32b also has a control valve 46a or 46b at the outlet side thereof between each conduit 40a or 40b and conduit 22. By selective opening and closing of control valves 44a or 44b and 46a or 46b, the path of refrigerant can be controlled through either tank 320 or 32b. in the description herebelow, the parallel elements in oil-scavenging system 20 are referred to with a and b used in conjuction with the identifying numeral:

a will identify the parts associated with the left tank shown in the drawing; b will identify parts associated with the right tank shown in the drawing. in the description, given below, it will be assumed that the operation starts at a given time and operates in a predetermined sequence as to time. It will be obvious, however, to all skilled in the art that the operation of the system of the invention can be initiated and controlled manually, by a pre-set time-schedule control means, or by various process-parameter sensing means, such as those based on pressure-sensing devices or by a combination of such means, all according to requirements of a particular operation.

In this description set forth below, all of valves 46a, 46b, 44a and 44b are normally open valves.

At the start of the operation of the scavenging system, valve 44b, in conduit 38b, is closed by the cycle timer control means 37, which is pre-scheduled, for example, to operate at the end of each week, means 37 controlling the valves through electric circuits and solenoids, or pneumatically, if desired. External heater 35b is actuated conveniently by means ofa thermostatically actuated control 48b, having a probe placed near the bottom flange of tank 32b. Heater 35b aids residual refrigerant in tank 32b, to be evacuated therefrom. After a short time delay to allow this evacuation of refrigerant, valve 46b is closed and internal heater 34b is activated, thereby isolating and warming tank 32b.

When valves 44b and 46b are both closed, then pressure control 45b opens valve 44b to relieve pressure and tends to back-flush any foreign material on the filter element 36.

As the heat liquefies the oil and causes it to drain to the bottom of the tank, the temperature in the vicinity of thermostat 48b increases markedly and signals thermostatically controlled oil drain valve 50b to open, thereby admitting the oil to oil-return conduit 52 leading to the compressor crankcase. After the oil has had an opportunity to drain, the heaters are turned off and valve 46b is opened.

As the refrigerant-cleaning and oil-scavenging sequence in the tank 32b ends, the master timer 37 operates to control the cleaning of tank 32a in an analogous manner. However, valve 44b in the refrigerant entrance line to tank 32b is kept closed for a short time after the heaters 34b and 35b cease to operate in order to allow environmental cooling to freeqe any remaining oil in the first tank 32b before valve 44b is open to accommodate normal refrigerant flow through that side of the system.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a refrigeration system of the type using an oillubricated reciprocating piston compressor and a refrigerant which is immiscible with the oil, the improvement comprising the incorporation in the liquid refrigerant piping system of a refrigerant-scrubbing system having:

a plurality of scrubbing tanks mounted in parallel relationship to one another;

filter means in said scrubbing tanks to collect immiscible oil from refrigerant flowing therethrough; valve means to direct refrigerant flow from one said scrubbing tank to another and to alternately isolate at least one said tank from said piping system; heating means associated with said scrubbing tanks causing said oil to liquefy during its isolation from said system; and

means for removing liquefied oil from said tank before returning said oil to said system.

2. A refrigeration system as specified in claim 1, wherein:

for each said scrubbing tank said heating means comprises an external heating means and an internal heating means, said external heating means forming means to evaporate refrigerant from said scrubbing tank before said tank is fully isolated from said refrigerant piping system;

said internal heating means forming means to liquefy frozen oil after said tank is fully isolated from said refrigerant piping system.

3. A refrigeration system as specified in claim 1, wherein:

said diverting of flow from tank to tank is controlled by a pre-scheduled timing system.

4. A refrigeration system as specified in claim 1, wherein:

a thermostatically controlled valve is utilized to remove liquefied oil from said isolated tank.

5. A process for scavenging immiscible lubricating oil from a refrigeration system of the type utilizing a reciprocating-piston compressor, said process comprising the steps of:

providing a plurality of filters mounted in parallel fashion in the liquid refrigerant piping;

flowing liquid refrigerant through a first filter for a predetermined time period while permitting a predetermined amount of oil build-up on said first filter;

automatically, at the end of said period, isolating said first filter from said liquid refrigerant flow to another said filter; and

heating oil in said first filter and removing it as a liquid therefrom before isolating said other filter and returning refrigerant flow through said first filter.

6. A process as specified in claim 5, wherein:

residual refrigerant is evaporated from a tank enclosing said first filter after flow of refrigerant thereto has been stopped, but before temperature therein is increased to liquefy said oil; and

residual liquefied oil is frozen before the tank is again fully incorporated into the liquid refrigerant piping line after liquefied oil has been removed therefrom.

7. A refrigeration system as specified in claim 1, 65 wherein:

all of said means are located on the low temperature side of said refrigeration system.

i t I t i 

1. In a refrigeration system of the type using an oil-lubricated reciprocating piston compressor and a refrigerant which is immiscible with the oil, the improvement comprising the incorporation in the liquid refrigerant piping system of a refrigerant-scrubbing system having: a plurality of scrubbing tanks mounted in parallel relationship to one another; filter means in said scrubbing tanks to collect immiscible oil from refrigerant flowing therethrough; valve means to direct refrigerant flow from one said scrubbing tank to another and to alternately isolate at least one said tank from said piping system; heating means associated with said scrubbing tanks causing said oil to liquefy during its isolation from said system; and means for removing liquefied oil from said tank before returning said oil to said system.
 2. A refrigeration system as specified in claim 1, wherein: for each said scrubbing tank said heating means comprises an external heating means and an internal heating means, said external heating means forming means to evaporate refrigerant from said scrubbing tank before said tank is fully isolated from said refrigerant piping system; said internal heating means forming means to liquefy frozen oil after said tank is fully isolated from said refrigerant piping system.
 3. A refrigeration system as specified in claim 1, wherein: said diverting of flow from tank to tank is controlled by a pre-scheduled timing system.
 4. A refrigeration system as specified in claim 1, wherein: a thermostatically controlled valve is utilized to remove liquefied oil from said isolated tank.
 5. A process for scavenging immiscible lubricating oil from a refrigeration system of the type utilizing a reciprocating-piston compressor, said process comprising the steps of: providing a plurality of filters mounted in parallel fashion in the liquid refrigerant piping; flowing liquid refrigerant through a first filter for a predetermined time period while permitting a predetermined amount of oil build-up on said first filter; automatically, at the end of said period, isolating said first filter from said liquid refrigerant flow to another said filter; and heating oil in said first filter and removing it as a liquid therefrom before isolating said other filter and returning refrigerant flow through said first filter.
 6. A process as specified in claim 5, wherein: residual refrigerant is evaporated from a tank enclosing said first filter after flow of refrigerant thereto has been stopped, but before temperature therein is increased to liquefy said oil; and residual liquefied oil is frozen before the tank is again fully incorporated into the liquid refrigerant piping line after liquefied oil has been removed therefrom.
 7. A refrigeration system as specified in claim 1, wherein: all of said means are located on the low temperature side of said refrigeration system. 